baciLlus coli 391 
would suggest that the Hberation of gas in sugar broth cultures of 
B. coli and other aerogenic bacteria depends upon the production 
of formic acid from the carbohydrate and its subsequent decomposi- 
tion into carbon dioxide and hydrogen by the action of an enzyme, 
formiase, in accordance with the equation II.COOH = a\ + H2. 
(c) Toxins.—^, coli usually does not produce a soluble toxin. 
Theobald Smith^ has shown, however, that twenty-four to forty-eight 
hour filtrates of broth cultures of B. coli obtained from the intestinal 
tracts of young cattle that have "scours," injected intravenously into 
calves cause severe symptoms. Feeding large amounts of culture are 
without effect. The injection of killed cultures into laboratory 
animals frequently causes death; if large amounts are introduced 
intravenously into rabbits there is usually a lowering of the body 
temperature, diarrhea, collapse and death even within three hours. - 
If the animals survive for a longer time a pin-ulent peritonitis may 
develop. Living cultures of colon bacilli derived from inflammatory 
processes in man are generally virulent for guinea-pigs. Old stock 
cultures are less virulent as a rule. The symptoms of toxemia which 
are exhibited by laboratory animals following the injection of colon 
bacilli are probably caused by the liberation of endotoxins from the 
bacilli. 
Pathogenesis.— The colon bacillus is a normal inhabitant of the 
intestinal tracts of man and the higher animals, although colon-like 
bacilli have been found upon grains of various kinds.^ Theobald Smith'' 
however, has shown that certain strains of B. coli are very pathogenic 
for calves. Rogers, Clark and Evans^ and Levine'' have shown that 
colonoid bacilli isolated from grains are comparatively rare in feces: 
the hydrogen-ion concentration produced by these strains after several 
days in glucose— phosphate solution is lower than that characteristic 
of fecal colon bacilli.'' They are alkaline to methyl red. 
Ordinarily the colon bacillus is a harmless parasite, but it may 
become invasive if conditions arise which weaken the intestinal mucosa. 
In peritonitis, purulent perforative appendicitis, angiocholitis, and 
even in occasional cases of pancreatitis, the organism is frequently 
isolated either in pure culture, or in association with other bacteria, 
as streptococci, typhoid bacilli, or staphylococci. It is difficult to 
determine with precision the part played by B. coli in these conditions. 
Occasional cases of enteritis are encountered which appear to be caused 
by this organism, other bacteria having been ruled out. The careful 
studies of Coleman and Hastings^ are of considerable importance in 
1 Jour. Exp. Med., 1927, 46, 123. 2 Escherich. Fort. d. Med., 1885, 3, 515. 
' Papasotiriu: Arch. f. Hyg., 1902, 41, 204. Prescott: Sedgwick Anniversary Vol- 
ume, 1906, p. 208. 
* Jour. Exp. Med., 1927, 46, 12.3. 
'■> Jour. Infec. Dis., 1914, 15, 100; 1915, 17, 137. 
« Ibid., 1916, 18, No. 4. ' Ibid., 1915, 17, 137. 
" Med. and Surg. Report of Bellevue and Allied Hospitals of the City of New York, 
1909-1910, 4, 56. 
